I don't think it's good to think of the value sent with `done: true` as "one of the values." It's in a different category, and not part of the yielded sequence. ________________________________ From: Mark Volkmann<mailto:[email protected]> Sent: 2015-04-05 18:43 To: Allen Wirfs-Brock<mailto:[email protected]> Cc: es-discuss list<mailto:[email protected]> Subject: Re: last value from iterator
Thanks, that helps. I had been thinking that for-of was a model for how iterators should be consumed. When implementing any kind of iterator (generator or not), it seems important to recognize that if you choose to return a value with done set to true, you are precluding the use of for-of with that iterator (assuming you want all the values). On Sun, Apr 5, 2015 at 11:40 AM, Allen Wirfs-Brock <[email protected]<mailto:[email protected]>> wrote: On Apr 5, 2015, at 6:04 AM, Mark Volkmann wrote: I thought that when an iterator returns done: true, the value should not be used. Why do you think that? The definition of the IteratorResult interface in the the ES6 spec. doesn't say that. However, if a generator function ends by returning a value, done will be true when that value is returned and the value should be used. Could be used. Whether a generator or any Iterator provides a meaningful value when it reach the the 'done' state depends upon its specific definition. Given this, how can a consumer know the correct way to handle the value when done is true? Clearly consumers shouldn't have to be aware of whether the iterator is actually a generator and whether it ends by returning a value. An Iterator does not have to be a generator to provide a 'done' state value. In general, If you are going to do anything other than basic iteration, such as is performed by for-of, you need to know about the specific Iterator you are using. Allen -- R. Mark Volkmann Object Computing, Inc.
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